HR: 0800h
AN: T11A-0341    [Abstracts]
TI: Dynamics of grains induced by the competition of coarsening and fragmentation
AU: * Mathiesen, J
EM: joachim.mathiesen@fys.uio.no
AF: Physics of Geological Processes, Univ. of Oslo, P.O. 1048 Blindern, Oslo, 0316, Norway
AU: Ferkinghoff-Borg, J
AF: Niels Bohr Institute, Univ. of Copenhagen, Blegdamsvej 17, Copenhagen, 2100, Denmark
AU: Jensen, M
AF: Niels Bohr Institute, Univ. of Copenhagen, Blegdamsvej 17, Copenhagen, 2100, Denmark
AU: Olesen, P
AF: Niels Bohr Institute, Univ. of Copenhagen, Blegdamsvej 17, Copenhagen, 2100, Denmark
AU: Svensson, A
AF: Niels Bohr Institute, Univ. of Copenhagen, Blegdamsvej 17, Copenhagen, 2100, Denmark
AB: We propose a dynamical model for the grain evolution in systems dominated by grain coarsening and fragmentation, or rotation recrystallization. Specifically, we formulate a generic rate equation for the size distribution of grains. As an example of the application of our equation, we employ data on the evolution of crystal assemblies from the North Greenland Icecore Project (NorthGRIP). The size distributions of ice crystals in the upper 880m of the ice core covers a time-span of approximately 5300 years and provide an excellent record of the grain evolution. Slowly, the size distributions evolve towards a universal curve and a steady state is reached where the fragmentation balances the coarsening. The model provides an excellent one-parameter fit of the steady state ice crystal distribution in terms of a Bessel function. The full dynamics is described by two parameters controlling the rate of coarsening and fragmentation, respectively.
DE: 0724 Ice cores (4932)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting